The capability of testing telephone lines and telephone equipment is a necessity in order to maintain high quality telephone service as well as to quickly detect faults, determine the problem and dispatch repairmen to remedy the problem. The testing of trunks, telephone lines and telephone sets was carried out early on by the use of a local test desk where personnel were able to establish a switched connection to provide a metallic test path directly to the subscriber line or telephone set. When the metallic test path was established, the test desk personnel could conduct simple continuity, resistance, capacitance, etc. measurements to determine the probable fault, or simply to ascertain that there was no imminent problem.
The usefulness of local test desk facilities, and the like, have by and large been antiquated, in view that telecommunication systems nowadays are highly developed and sophisticated computer or processor driven system that provide the switching of voice and data signals without the use of any metallic paths. Hence, simple DC and AC current and voltage tests can no longer be carried out via metallic paths with intervening switching systems between the test equipment and lines or telephone equipment to be tested. A similar aggravation to this test problem is the use of digital carrier systems which are often utilized between central offices and telephone subscribers. With digital carrier systems, such as the well-known T1 carrier system, the communication paths that exist between the central office and the subscribers carry multiplexed digital signals, and thus cannot be utilized for conventional DC or AC line tests. Digital carrier systems thus had to be equipped with ancillary metallic paths dedicated to testing of the lines. The dedicated test paths then necessitated additional connections and equipment for connecting to remote test equipment.
In order to accommodate the testing of both the carrier system, including the central office terminal (COT) and an associated remote terminal (RT) there is in widespread use a pair gain test controller that provides a test interface between a loop carrier system and a loop testing system. The pair gain test controller is situated in a central office switching system and is responsive to a maintenance center to provide a connection to a DC test pair, which comprises a metallic path, that extends from the central office out to the remote terminal. The DC test pair is switchably connected by the remote terminal so that DC and other conventional tests can be carried out on the customer loop. The pair gain test controller can also conduct certain tests on the channel units of the carrier system.
While the pair gain test controller is adequately adapted for carrying out tests on the carrier systems and the customer loops, such system is required to be situated in a central office, and cannot carry out sophisticated automated tests. As a result, a need exists for methods and apparatus for conducting more sophisticated and accurate tests on telephone equipment to determine the operability thereof. Another need exists for test equipment that can be situated at a location remote from the central office and communicate with a carrier remote terminal so that tests can be conducted on the subscriber equipment. A further need exists for a sophisticated processor-controlled test system that provides highly accurate test signals to the line under test, and provides a high degree of flexibility and accuracy in processing the signals received from the line under test.